Influence of oxygen enrichment on air-gasification of sawdust in an innovative rotating grate downdraft gasifier

Abstract

This paper reports an experimental study on the influences of oxygen enrichment on gasification operating and performance parameters. The experiments were conducted using a downdraft gasifier with constricted throat and a rotating grate retrofits. The innovative rotating grate allows uninterrupted charging of fresh biomass feedstock (sawdust) through the gasifier throat and in a like manner dislodges ash and charred material which would otherwise form a lump on the grate and eventually clogged gasifier system. The flow rate of gasification medium was maintained at 10 liters per minute (LPM) while varying the percentage weight composition of oxygen in the air at 21, 30, 40, 50, 60 and 80%. Result obtained showed that 60% oxygen enrichment generated producer gas the highest proportion of carbon monoxide (CO) as well as hydrogen (H2) amounting to 29.57% and 14.29% respectively. The producer gas Lower Heating Value (LHV) was observed to rise consistently from 2.08 to a maximum of 9.02MJ/Nm3 as percentage composition of oxygen in gasification medium (air/oxygen) was increased from 21% to 60%. General observation indicated that oxygen enrichment favors higher gasification temperature, improves producer gas quality in terms of LHV and as well the overall gasification performance.

Keywords: Biomass, Gasification, Sawdust, Downdraft gasifier, Producer gas